Soft tissue balancing in robotic knee surgery

ABSTRACT

A system and method may be used to evaluate soft tissue. A knee arthroplasty soft tissue evaluation may use an adjustable spacer, such as varying sized physical spacers or an inflatable bladder, along with a sensor to measure force, pressure, gap distance, or the like during a range of motion test. A method may include maintaining an equal pressure or gap distance for a medial component and a lateral component of an adjustable spacer during a range of motion test. Information, including, for example a maximum or minimum gap distance or pressure may be determined during the range of motion test. The determined information may be output for display or used to update a surgical plan.

CLAIM OF PRIORITY

This application claims the benefit of priority to U.S. ProvisionalApplications Nos. 62/625,706, filed Feb. 2, 2018, titled “SOFT TISSUEBALANCING IN ROBOTIC KNEE SURGERY”; and 62/697,227, filed Jul. 12, 2018,titled “SOFT TISSUE BALANCING IN ROBOTIC KNEE SURGERY”; each of which ishereby incorporated herein by reference in its entirety.

BACKGROUND

Computer-assisted surgery has been developed in order to help a surgeonin altering bones, and in positioning and orienting implants to adesired location. Computer-assisted surgery may encompass a wide rangeof devices, including surgical navigation, pre-operative planning, andvarious robotic devices. One area where computer-assisted surgery haspotential is in orthopedic joint repair or replacement surgeries. Forexample, soft tissue balancing is an important factor in articularrepair, as an unbalance may result in joint instability. However, whenperforming orthopedic surgery on joints, soft tissue evaluations areconventionally done by hand, with the surgeon qualitatively assessingthe limits of patient's range of motion. The conventional technique mayresult in errors or lack precision.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which are not necessarily drawn to scale, like numeralsmay describe similar components in different views. Like numerals havingdifferent letter suffixes may represent different instances of similarcomponents. The drawings illustrate generally, by way of example, butnot by way of limitation, various embodiments discussed in the presentdocument.

FIG. 1 illustrates a force sensor device used with a robotic arm inaccordance with some embodiments.

FIGS. 2-3 illustrate surgical planning user interfaces in accordancewith some embodiments.

FIG. 4 illustrates an eLibra device with various spacers in accordancewith some embodiments.

FIGS. 5-6 illustrate calibration user interfaces in accordance with someembodiments.

FIG. 7 illustrates a system for using an eLibra device in accordancewith some embodiments.

FIG. 8 illustrates a force measurement display user interface inaccordance with some embodiments.

FIG. 9 illustrates an adjustable spacer in accordance with someembodiments.

FIG. 10 illustrates a surgical technique in accordance with someembodiments.

FIG. 11 illustrates an adjustable spacer with independently adjustablemedial and lateral components in accordance with some embodiments.

FIG. 12 illustrates an adjustable spacer and graphs showing effects ofthe adjustable spacer in accordance with some embodiments.

FIG. 13 illustrates a system for using an adjustable spacer with arobotic surgical device in accordance with some embodiments.

FIG. 14 illustrates a unicondylar adjustable spacer used in a partialknee arthroplasty in accordance with some embodiments.

FIG. 15 illustrates a flowchart showing a technique for using anadjustable spacer in a surgical knee procedure in accordance with someembodiments.

FIG. 16 illustrates a system for performing techniques described herein,in accordance with some embodiments.

FIG. 17 illustrates a block diagram of an example of a machine uponwhich any one or more of the techniques discussed herein may perform inaccordance with some embodiments.

DETAILED DESCRIPTION

Systems and methods for soft tissue balancing in robotic kneearthroplasty are provided herein. Knee arthroplasty techniques maybenefit from the use of a robotic device to assist in the surgery. Oneaspect of knee arthroplasty includes checking knee alignment andkinematics throughout a range of motion of the knee. As the knee moves,gap distance or tension on ligaments may be measured to determinekinematics and alignment. In an example, a spacer may be inserted intothe knee during a range of motion test to maintain a particular tensionor gap distance while kinematics or alignment are checked. The spacermay be an electronic device, such as described below, to transmit forceor tension information. In another example, the spacer may beadjustable, such that the adjustable spacer may maintain a fixedpressure or gap distance during a range of motion test. In an example, aspacer may maintain different forces or gap distances on a medial versusa lateral side of the knee.

FIG. 1 illustrates a force sensor device used with a robotic arm inaccordance with some embodiments. Systems and techniques describedherein include adapting for wireless communication an eLibra dynamicknee balancing system provided by Synvasive Technology, Reno, Nev. foruse with the Medtech SA ROSA robotic surgical system for total andpartial knee arthroplasty.

As shown in FIG. 1, an eLibra device 102 wirelessly transmits force andtension data captured by the eLibra device to a robotic device 104. TheeLibra device 102 may track, via onboard accelerometers and gyroscopes,the relative orientation of the eLibra device 102 which, combined withthe optical tracking system of the robotic device 104 (e.g., a MedtechROSA robot) allows a graph to be shown as displayed on FIG. 1 of theforces in the medial and lateral compartments of the knee throughout therange of motion.

The method of balancing the knee in total knee arthroplasty using thiscombination of eLibra and the ROSA knee application may works asdescribed below.

Before performing any of the femoral resections in a knee arthroplasty,the tension of the knee may be checked using a trial device. As shown inFIG. 2, a knee planning screen of a robotic device application isdescribed showing the intended v/v (varus/valgus) of the femoralcomponent, v/v of the tibial cut, the thickness of the distal resectionon the medial compartment, the distal resection of the lateralcompartment, the proximal resections of both the medial and lateralcompartments, or the posterior resections of the medial and lateralcompartments, in an example.

The planning screen may show the posterior slope and an angle value forflexion that represents the flexion value used in planning the resectionshowed in FIG. 2.

FIG. 3 shows an example of how the information from the eLibra device isincorporated into the planning screen of the robotic knee application.On the left hand side of FIG. 3, the values for the eLibra spacer'srecorded force are displayed with 62 Newtons in the medial compartmentand 77 Newtons in the lateral compartment. These force values are whatare predicted to occur in an example where the surgeon performsresections according to the plans developed herein in FIG. 5 and FIG. 6.

As shown in FIG. 3, in this example, with the knee in 27 degrees offlexion and 2 degree of varus, using a spacer with the eLibra device ofsize 4 in extension resulted in 62 Newtons of force and using a spacersize of −1 in extension resulted in 77 Newtons of force in this example.

As shown in FIG. 4, this eLibra spacer values can be accomplished byusing shims of variance sizes from −4 mm to −3, −2, −1, 0 mm and so on,to positive one, positive 2, positive 3, positive 4 millimeters.

Alternatively, as shown in FIG. 9, rather than using shims, anadjustable spacer tool, similar to those described in U.S. Pat. No.9,808,356 to Synvasive Technology may be used to adjust platform heightsof the medial and lateral compartments via rotation of a screw orscrews. Platform adjustment can also occur via electrometrical means,potentially under control of the robotic device. For example, the arobot system may wirelessly adjust the heights of the medial and lateralcompartments of the adjustable spacer as the knee is moved through arange of motion, by detecting the change in orientation of the leg withoptical tracking.

FIG. 5 shows how the resections of a total knee replacement can beplanned using the eLibra spacer and recorded flexion and positioningvalues.

In this example, on the medial compartment, bone cuts of 15 millimeterstotal (8.0 distal+7.0 proximal) are planned. With the planned implantsize of 19 millimeters the plan would therefore result in an overstuffof the medial compartment of 4 millimeters. Thus, in order to test andmeasure the tension forces in the medial compartment with this plannedresection, the eLibra device should be loaded with a spacer size of 4millimeters in the medial compartment.

In the lateral compartment, in order to test the tension experiencedusing these planned resections, the combination of the proximal anddistal resections of 10 millimeters each result in planned bone cuts of20 millimeters total. With a planned implant size of 19 millimeters thiswould therefore result of laxity and understuff of 1 millimeter in thelateral compartment and a thus −1 millimeter eLibra spacer would be usedto measure the forces experienced with this planned cut (FIG. 5) inextension.

In Flexion as shown in FIG. 6, here the plan calls for a posteriorresection of 9 millimeters and a proximal resection of 7 millimeters,thus totaling planned bone cuts in the medial compartment of 16millimeters. The implant size again being 19 millimeters would result inoverstuff of 3 millimeters in the medial compartment and the eLibraspacer then necessary to measure the forces experienced in flexion underthese planned resections would be 3 millimeters.

Similarity on the lateral side, with bone cuts planned of 17millimeters, 10 on the proximal section and 7 on the posteriorresection, an implant size of 19 millimeters would therefore result inan overstuff of 2 millimeters in the lateral compartment and thereforean eLibra spacer size of 2 millimeters would be required in order toaccurately measure tensions experienced under these planned resections.

The surgeon may adjust the planned resections, test and record theforces captured by the eLibra device in flexion and extension, and thenrepeat as necessary until the plan results in the desired expectedtension values. The surgeon may then perform the femoral resectionsaccording to the final plan.

Once the cuts are done, the resections are complete according to theplanned values, and tension may be confirmed over the entire range ofmotion with trial implants such as described in patent applicationsrelated to the eLibra device (e.g. U.S. application Ser. No. 13/709,506,incorporated herein by reference in its entirety).

As shown in FIG. 7, the eLibra device may be inserted in between thefemur and tibia and the patient's leg can be moved throughout the rangeof motion from flexion to extension and the eLibra device will record(or the CAS system of the ROSA robot will record) force valuesthroughout the range of motion. The force (in Newtons) experienced inthe medial compartment is a solid line and the lateral compartment is adotted line in FIG. 8. The angular values for flexion are captured byvirtue of the angular tracking of the eLibra device, which may beperformed using an additional sensor, such as an inertial measurementunit (IMU), an accelerometer, a gyroscope, or the like, or the trackingof the robotic device (which may track the degree of flexion/extensionof the patient's leg by optical tracking of the femur and tibia or usingcontact with a portion of the knee to track the knee using the roboticdevice's internal accelerometer or gyroscope).

Systems and methods for using an adjustable spacer for a surgical kneeprocedure, such as evaluating soft tissue during a knee arthroplasty aredescribed herein. The systems described herein may include using anadjustable spacer with independently adjustable components (e.g., amedial component and a lateral component) for soft tissue evaluation. Inan example, the independently adjustable components may be controlledusing independent pressure or independent gap distance during a softtissue evaluation. The adjustable spacer systems and methods describedherein may be used with a robotic surgical device.

Robotics offer a useful tool for assisting the surgeon in the surgicalfield. A robotic device may assist in the surgical field performingtasks such as biopsies, electrode implantation for functional procedures(e.g., stimulation of the cerebral cortex, deep brain stimulation), openskull surgical procedures, endoscopic interventions, other “key-hole”procedures, arthroplasty procedures, such as total or partial kneereplacement, hip replacement, shoulder implant procedures, or the like.In an example, a surgical procedure may use a surgical robot. Thesurgical robot may include a robotic arm for performing operations. Atracking system may be used to determine a relative location of thesurgical robot or robotic arm within a coordinate system or a surgicalfield. The surgical robot may have a different coordinate system ortracking system (e.g., using known movements of the surgical robot). Therobotic arm may include an end effector of the robotic arm of thesurgical robot, which may use sensors, such as a gyroscope,magnetoscope, accelerometer, etc. In an example, a processor may be usedto process information, such as tracking information, operationparameters, applied force, location, or the like.

FIG. 10 illustrates a surgical technique 1000 in accordance with someembodiments. The technique 1000 uses a robotic surgical device to assistin surgical procedures, such as a resection, a range of motion test, ora soft tissue balancing test. The technique 1000 includes initiating a3D plan, such as using a user interface of the robotic surgical device(e.g., the Medtech SA ROSA robotic surgical system). The technique 1000includes an operation to perform a tibial cut, for example using theROSA or other robotic arm for a total or partial knee arthroplasty. Thetechnique 1000 includes an operation to capture balance during a rangeof motion test, for example using an inflatable device or a robotic arm.The inflatable device is described in more detail below.

The technique 1000 may include using feedback from the range of motiontest to adjust the plan (e.g., automatically change a parameter of thepreoperative plan based on the range of motion test, such as balanceinformation, a maximum or minimum distance, range of motion, or angel).The technique 1000 may include performing a distal cut, such as usingthe robotic arm. The technique 1000 may include evaluating balance insoft tissue, such as flexion or extension balance using the inflatabledevice, or the robotic arm (e.g., the Rosa robotic arm with a toolattached to an end effector on a distal end of the robotic arm).

In an example, the technique 1000 may include using an optical trackerto track components of a surgery. For example, tracked components mayinclude a femur, a tibia, a robotic arm (e.g., an end effector attachedto a distal end of the robotic arm), a tool, or the like. The technique1000 may include performing a range of motion test to evaluate softtissue tension, pressure, or gap distance in a knee joint in the rangebetween extension and flexion. Optical trackers may be used to determinevarious attributes of bones or soft tissue during the range of motiontest. For example, distance traveled by the tibia (or femur) throughoutthe range of motion test, angle of bone during the range of motion test(e.g., maximum flexion angle or maximum extension angle), gap distanceat various points or throughout the range of motion test (which mayinclude separate medial and lateral gap distances or a combined ormaximum gap distance throughout), or the like.

In an example, the gap distance may be shown on a user interface duringthe range of motion test. The gap distance may be shown based on aplanned resection (or resections, such as a tibial cut or a femoralcut). The planned resection may be shown on the user interface, alongwith gap distances throughout the range of motion test to displaydifferences or issues that may arise based on the planned resection andthe evaluated gap distances. In an example, potential errors arise whenusing the gap distance with un-resected bone (e.g., the surface of thebone) because the ultimate gap distances for the resected knee do notinclude the surface errors. For example, osteophytes may cause issueswith gap measurement, a varus deformity may impact laxity, an errorstate may impact gap measurement, or the lateral and medial laxity froma spacer tool may cause measurement issues (e.g., because the ligamentsare on the side, the measured laxity may differ from the actual laxitybecause of the rotation).

The technique 1000 may include establishing the preoperative plan andshowing the knee with the planned resections on the user interface. Thenas gap distances are determined throughout the range of motion test, thegap distances are displayed on the user interface with the plannedresections. This combination of preplanned resection visualization withactual measured gap distance information allows for evaluation of theplanned resections with real gap distance feedback. This combinationalso allows for evaluating the ultimate gap distances with the plannedresection rather than gap distances pre-resection, which may notultimately be accurate. The combination further allows for accurateplanning of what the soft tissue balancing (e.g., rotation of the femurrelative to the tibia) will be after the planned resection withoutneeding to actually perform the resection. This allows for accurateplanning, and modification to the resection may be made.

In an example the technique 1000 may include displaying the measured andactual gap distances with the planned resection by reference to a plane(e.g., the tibial resection plane or a femur horizontal plane). In anexample, the femur horizontal plane may be used along with a determinedtibial plane a few degrees offset from the femur horizontal plane. Inanother example, the tibial cut may be performed before the range ofmotion test. The cut tibial plane may be used, or may be offset by a fewmm for the femur plane. In an example, the femur horizontal plane may beused because it is agnostic to movement of the bone, throughout therange of motion (e.g., laxity independent or laxity based on resection,not where bone sits or the femur horizontal plane).

In an example, when expanding the knee, ligaments may be on a side whichcauses issues with measurement of the gap distance or soft tissuebalance. Using the preplanned resection with measured gap distance, andtaking into account the plane used for reference, the measurement may bemade in a more consistent manner.

In an example, the range of motion test may include registering thetibia with reference to a bone model (e.g., a preoperative plan), andregistering a tracker for the tibia (the femur may be registered andtracked as well. The range of motion test is then performed. The tibiais tracked throughout the range of motion test (e.g., by tracking thegap from the planned resection of the femur or tibia to the femur ortibia throughout the range of motion). The gap distance at a point orthroughout a range (e.g., a maximum gap distance, an animation of gapdistance throughout the range of motion, or a gap distance at aselectable angle of range of motion) may be displayed on the userinterface. The user interface may show the gap distance from thepreplanned resection to the femur (e.g., instead of from the unresectedtibia to the unresected femur).

The gap distance may be measured using the optical trackers, may use anadjustable spacer as described throughout this disclosure, such as anindependently adjustable medial and lateral spacer, or a position sensor(e.g., iAssist). Because a natural rotation may occur during the rangeof motion test, using an independently adjustable medial and lateralspacer may allow for different gap distances to be measured throughoutthe range of motion.

FIG. 11 illustrates an adjustable spacer 1102 with independentlyadjustable medial and lateral components (1104 and 1106, respectively)in accordance with some embodiments. The adjustable spacer 1102 may beused within a knee, such as for a total or partial knee arthroplasty(e.g., as described above with respect to FIG. 10). The adjustablespacer 1102 may be used to measure, determine, or change a gap distanceor pressure difference between a femur and a tibia of a patient. Forexample, the adjustable spacer 1102 may be placed between the tibia andthe femur (e.g., after a tibial resection as described above duringtechnique 1000) and inflated to measure gap distance or pressure, forexample throughout a range of motion test.

The adjustable spacer 1102 may be inflated by one or more pumps (e.g.,medial pump 1105 or lateral pump 1107, or a single pump with a valveconfigured to control whether the medial component 1104 or the lateralcomponent 1106 is inflated). The medial component 1104 and the lateralcomponent 1106 of the adjustable spacer 1102 may be independentlyinflated, adjusted (e.g., undergo an increase in inflation or bedeflated), or controlled (e.g., pressure maintenance).

The medial component 1104 and the lateral component 1106 of theadjustable spacer 1102 may be inflated independently to a particular gapdistance. For example, as shown in the example in FIG. 11, on the leftside the medial component 1104 is inflated to 18 millimeters (mm), andthe lateral component 1106 is inflated to 12 millimeters. These gapdistances may correspond to internal forces, as shown on the right sideof FIG. 11. The example in FIG. 11 shows a pressure of 35 Newtons (N) inthe medial component 1104 and 52 Newtons in the lateral component 1106.The gap distances and forces may further correspond to pressure appliedby one or more pumps. For the example of FIG. 11, the medial pump 1105is applying 7 pounds per square inch (psi) of pressure, corresponding tothe 35 N, which may also correspond to 18 mm of gap distance. Thelateral pump 1107 applies 12 psi, corresponding to 52 N and 12 mm gapdistance. In an example, a surgeon may spread the knee to a desiredforce with the adjustable spacer 1102 and the femoral rotation requiredto achieve balance between the medial and lateral sides may be output ona user interface.

The adjustable spacer 1102 may include one or more sensors, such as aHall effect sensor, to accurately measure the gap distance in the medialcomponent 1104 or the lateral component 1106. For example, the medialcomponent 1104 and the lateral component 1106 may each have a Halleffect sensor to independently measure gap distance in the respectivecomponents. In an example, a Hall effect sensor may output a voltagecorresponding to a change in magnetic field based on the gap distance.For example, a magnet may be placed on a free end of the medial 1104 orlateral 1106 component, and a Hall effect sensor may be used todetermine the change in distance of the component 1104 or 1106 based onthe change in magnetic field from the free end being displaced from abase of the adjustable spacer 1102. In this example, the Hall effectsensor may be located on the base of the adjustable spacer 1102 (e.g.,on an end opposite the free end of one of the components 1104 or 1106).

The medial pump 1105 or the lateral pump 1107 may be controlled by apump controller. The pump controller may be coupled to, operated by, orlocated within a robotic surgical device (e.g., ROSA). For example, thepump controller may be executed using a processor of the roboticsurgical device. A user interface of a display of the robotic surgicaldevice (or an external display) may be used to display information(e.g., gap distance, force, pressure, etc.) related to the adjustablespacer 1102, the pump controller, or the medial/lateral pumps 1105/1107.

The gap distance in the medial or lateral component of the adjustablespacer may be determined using a distance sensor, such as a Hall effectsensor. In an example, one distance sensor may be used, such as in acentral location of the medial or lateral component. In another example,two distance sensors may be used, such as at either end of the medial orlateral component. In another example, three sensors may be used (e.g.,with a sensor shown at 1108), such as one in a central location and twoat either end of the medial or lateral component. Other configurationsof sensors (e.g., at corners of a component, in the middle of acomponent) may be used to increase accuracy of gap distancemeasurements. Other measurement techniques may be used, including usingoptical tracking of the gap distance, a time-of-flight sensor, a tensionsensor, or the like. The sensor measurements for gap distance may beused on the adjustable spacer of FIG. 9 similarly.

FIG. 12 illustrates an adjustable spacer (1202 and 1204) and graphs 1200and 1201 showing effects of the adjustable spacer (1202 and 1204) inaccordance with some embodiments. The adjustable spacer (1202 and 1204)may be used within a knee, such as for a total or partial kneearthroplasty. The adjustable spacer (1202 and 1204) may be used tomeasure, determine, or change a gap distance or pressure differencebetween a femur and a tibia of a patient. For example, the adjustablespacer (1202 and 1204) may be placed between the tibia and the femur(e.g., after a tibial resection) and inflated to measure gap distance orpressure, for example throughout a range of motion test.

The adjustable spacer is shown in a first controlled configuration 1202corresponding to graph 1200 and a second controlled configuration 1204corresponding to graph 1201. The first configuration 1202 includescontrolling the adjustable spacer such that the pressure in a medialcomponent and a lateral component of the adjustable spacer are fixed. Afixed pressure means that the pressure output from a pump or pumps isequal (e.g., 7 psi) to each component, medial and lateral of theadjustable spacer. Said another way, the medial and lateral componentsof the adjustable spacer are free to change gap distance (e.g., haveunequal gap distance), but have the same pressure applied (air or otherfluid applied within a bladder of each component). The fixed pressuremay also result in equal force (e.g., 35 N) within each component (e.g.,as applied to a free end from a fixed end, shown in FIG. 12 with anupward arrow).

Graph 1200 illustrates changes in gap distance for the fixed pressureadjustable spacer 1202 throughout a range of motion test. Graph 1200 hasan x-axis illustrating degrees of the range of motion test (e.g.,starting at zero degrees for a fully extended knee, and moving up indegrees towards flexion). The y-axis of graph 1200 illustrates a gapdistance (e.g., in the example shown in FIG. 12, fluctuating between 15and 25 mm). The gap distance is shown on graph 1200 in the medialcomponent (M) and the in the lateral component (L) of the adjustablespacer 1202 separately. The graph 1200 may be output to a user interfaceon a display (e.g., a display of a robotic surgical system) forevaluation by a surgeon. In an example, a maximum or minimum gapdistance for each component may be determined from the range of motiontest. The maximum or minimum gap distance (in either component or amaximum or minimum in both components) may be used to adjust a surgicalplan (e.g., a preoperative plan), such as by changing a parameter for aplanned resection of the femur, changing an implant size, or adjustingsoft tissue (e.g., releases). The changes to the preoperative plan maybe made automatically, for example changing a parameter of a plannedresection by a robotic arm.

The second configuration 1204 includes controlling the adjustable spacersuch that the gap distances in the medial component and the lateralcomponent of the adjustable spacer are fixed. A fixed gap distance meansthat the pressure output from a pump or pumps varies (e.g., 7 psi and 12psi as shown in FIG. 12) to each component, medial and lateral of theadjustable spacer. The medial and lateral components of the adjustablespacer are thus fixed to a certain gap distance, which may be determinedas part of a preoperative plan or interoperative change to apreoperative plan. The change in pressure may be adjusted during a rangeof motion test to retain the equal gap distance between the twocomponents. The change in pressure may correspond to a change in force(e.g., 35 N for 7 psi and 52 N for 12 psi), as applied to a free endfrom a fixed end, shown in FIG. 12 with an upward arrow.

Graph 1201 illustrates changes in pressure for the fixed equal gapdistance in components of the adjustable spacer 1202 throughout a rangeof motion test. Graph 1201 has an x-axis illustrating degrees of therange of motion test (e.g., starting at zero degrees for a fullyextended knee, and moving up in degrees towards flexion). The y-axis ofgraph 1201 may illustrate a pressure (e.g., applied from a pump) or aforce applied by the or within each component (e.g., in the exampleshown in FIG. 12, a force is illustrated). The pressure change is shownon graph 1201 in the medial component (M) and the in the lateralcomponent (L) of the adjustable spacer 1202 separately. The graph 1201may be output to a user interface on a display (e.g., a display of arobotic surgical system) for evaluation by a surgeon. In an example, amaximum or minimum pressure for each component may be determined fromthe range of motion test. The maximum or minimum pressure (in eithercomponent or a maximum or minimum in both components) may be used toadjust a surgical plan (e.g., a preoperative plan), such as by changinga parameter for a planned resection of the femur, changing an implantsize, or adjusting soft tissue (e.g., releases). The changes to thepreoperative plan may be made automatically, for example changing aparameter of a planned resection by a robotic arm.

In an example, only one side of the adjustable spacer 1202 (e.g., medialor lateral) may be inflated. The singly inflated side may be used toperform a stress test for the knee joint. During a stress test (whichmay be performed before or after a tibial cut), the lateral or themedial side may be inflated to assess ligament tension and find a gapdistance for that side. The stress test for one or both sides (medialand lateral) inflated, one at a time, may be conducted instead of or inaddition to a range of motion test with both sides (medial and lateral)inflated.

FIG. 13 illustrates a system 1300 for using an adjustable spacer with arobotic surgical device in accordance with some embodiments. The system1300 may include a robotic surgical system or device (e.g., a ROSArobotic surgical system), which may include a user interface and arobotic arm. The robotic surgical system or device may include a pump,be configured to hold or support a pump, interface with a pump, or thelike. In another example, the system 1300 may include a pump separatefrom the robotic surgical system or device. The pump (which may includemore than one pump) may be used to control an adjustable spacer. In theexample where the pump is controlled by the robotic system or device, aprocessor of the robotic system or device may control pressure output toone or more components of the adjustable spacer. The robotic surgicalsystem or device may be used to control the pump during a range ofmotion test, such as to evaluate gap distance or pressure in a medial orlateral component of the adjustable spacer.

FIG. 14 illustrates a unicondylar adjustable spacer used in a partialknee arthroplasty in accordance with some embodiments. The diagram 1400illustrated in FIG. 14 shows a unicondylar adjustable spacer, which maybe inflated or adjusted using a pump (e.g., controlled by a roboticsurgical system). In another example, an adjustable spacer with bothmedial and lateral components may be used, such as by only inflating oneside when used with a partial knee arthroplasty or when doing aunicondylar surgery on both the medial and the lateral sides of a singleknee. The singularly inflated component may be used during a range ofmotion test, holding gap distance to a specific gap distance or holdingpressure to a specific pressure (e.g., a specific gap distance orspecific pressure from a surgical plan). A minimum tension may bedetermined during the range of motion test. The minimum tension may beoutput, such as for display on a user interface or for use inautomatically adjusting a parameter of a surgical plan.

FIG. 15 illustrates a flowchart showing a technique 1500 for using anadjustable spacer in a surgical knee procedure in accordance with someembodiments. In an example, the technique 1500 may be performed after aninitial tibial cut. In another example, the technique 1500 is performedbefore any cuts during a knee arthroplasty. The technique 1500 may beperformed using a robotic surgical device. The inflation operationsdescribed below may be performed using a pump, which may beautomatically controlled by a pump controller of the robotic surgicaldevice. The robotic surgical device may include a display to present auser interface for presenting results of the technique 1500.

The technique 1500 includes an operation 502 to inflate a firstadjustable component of an adjustable spacer to separate a femur and atibia of a knee, for example on a medial side of a patient. Thetechnique 1500 includes an operation 504 inflate a second adjustablecomponent of the adjustable spacer to separate the femur and the tibiaof the knee, for example on a lateral side of the patient. In anexample, the second adjustable component is independently adjustable tothe first adjustable component.

The technique 1500 includes an operation 506 to select whether to use anequal pressure or an equal gap distance in the adjustable components.The equal pressure or equal gap distance may be determined using apreoperative plan. The technique 1500 includes an operation 508 when theequal pressure is selected. Operation 508 includes, during a range ofmotion test, maintaining an equal pressure in the first adjustablecomponent and the second adjustable component by allowing a medial gapdistance between the femur and the tibia caused by the first adjustablecomponent or a lateral gap distance between the femur and the tibia thesecond adjustable component to change.

The technique 1500 includes an operation 510 to, when the equal pressureis selected, determine a maximum gap distance during the range of motiontest. The maximum gap distance may be determined using a sensor (e.g., aHall effect sensor) or using optical tracking of the femur and thetibia. The technique 1500 includes an operation 512 when the equal gapdistance is selected. Operation 512 includes, during a range of motiontest, maintaining an equal gap distance between a medial gap of the kneecaused by the first adjustable component and a lateral gap of the kneecaused by the second adjustable component by increasing or decreasingpressure in the first adjustable component or the second adjustablecomponent.

The technique 1500 includes an operation 514 to, when the equal gapdistance is selected, determine a maximum pressure during the range ofmotion test. The maximum pressure may be determined using a sensor(e.g., a pressure sensor such as an eLibra device) or using feedback ata pump used to inflate the components. The technique 1500 includes anoperation 516 to output results for display on a user interface, such asthe maximum gap distance or the maximum pressure. In another example,results may be used to adjust a preoperative plan. For example, theresults may be used to determine an implant based on a maximum gapdistance (e.g., lateral or medial or both). The technique 1500 mayinclude repeating a range of motion test, for example after increasingor decreasing the equal pressure or the equal gap distance. In anexample, an implant with different heights for each side may be used,for example based on the pressure changes throughout the range ofmotion.

In an example, the pressure and the gap distance may be allowed tochange during the range of motion test. In this example, a 3D plan(e.g., a preoperative plan) may be used to set limits or targets for gapdistance or pressure. For example, a maximum pressure may be set fordifferent angles (e.g., from extension to flexion) or a maximum gap maybe set. In an example, operation 506 may include a determination to usethe 3D plan. The technique 1500 may then proceed to operation 511 to,during a range of motion test, maintain a gap distance or pressure basedon the 3D plan. At some portions of the range of motion test, the gapdistance may be held constant while at other portions of the range ofmotion test, the pressure may be held constant, according to the 3Dplan. The technique 1500 may include an operation 515 to determine amaximum pressure or maximum gap distance during the range of motion test(e.g., at different portions of the test, based on when the gap distanceor the pressure is held constant, respectively).

FIG. 16 illustrates a system 600 for performing techniques describedherein, in accordance with some embodiments. The system 600 includes arobotic surgical device 602 coupled to a pump 604, which may be used tocontrol a spacer device 606. The spacer device 606 includes a medialadjustable component 608 and a lateral adjustable component 612. Thesystem 600 may include a display device 614, which may be used todisplay a user interface 616. The system 600 may include a controlsystem 618 (e.g., a robotic controller), including a processor 620 andmemory 622. In an example, the display device 614 may be coupled to oneor more of the robotic surgical device 602, the spacer device 606, orthe control system 618.

In an example, the display device 614 may be used to display results ofa soft tissue procedure on the user interface 616. The results mayinclude gap distance or pressure information, such as over differentangles during a range of motion test. The gap distance or pressureinformation may be derived from a sensor, such as a sensor 610, whichmay be on the medial adjustable component 608 or the lateral adjustablecomponent 612 or elsewhere on or within the spacer device 606. Thesensor 610 may be a Hall effect sensor. The gap distance or pressureinformation may be related to a knee joint, and the range of motion testmay be performed from extension to flexion (or vice versa).

FIG. 17 illustrates a block diagram of an example machine 1700 uponwhich any one or more of the techniques discussed herein may perform inaccordance with some embodiments. In alternative embodiments, themachine 1700 may operate as a standalone device or may be connected(e.g., networked) to other machines. In a networked deployment, themachine 1700 may operate in the capacity of a server machine, a clientmachine, or both in server-client network environments. In an example,the machine 1700 may act as a peer machine in peer-to-peer (P2P) (orother distributed) network environment. The machine 1700 may be apersonal computer (PC), a tablet PC, a set-top box (STB), a personaldigital assistant (PDA), a mobile telephone, a web appliance, a networkrouter, switch or bridge, or any machine capable of executinginstructions (sequential or otherwise) that specify actions to be takenby that machine. Further, while only a single machine is illustrated,the term “machine” shall also be taken to include any collection ofmachines that individually or jointly execute a set (or multiple sets)of instructions to perform any one or more of the methodologiesdiscussed herein, such as cloud computing, software as a service (SaaS),other computer cluster configurations.

Machine (e.g., computer system) 1700 may include a hardware processor1702 (e.g., a central processing unit (CPU), a graphics processing unit(GPU), a hardware processor core, or any combination thereof), a mainmemory 1704 and a static memory 1706, some or all of which maycommunicate with each other via an interlink (e.g., bus) 1708. Themachine 1700 may further include a display unit 1710, an alphanumericinput device 1712 (e.g., a keyboard), and a user interface (UI)navigation device 1714 (e.g., a mouse). In an example, the display unit1710, input device 1712 and UI navigation device 1714 may be a touchscreen display. The machine 1700 may additionally include a storagedevice (e.g., drive unit) 1716, a signal generation device 1718 (e.g., aspeaker), a network interface device 1720, and one or more sensors 1721,such as a global positioning system (GPS) sensor, compass,accelerometer, or other sensor. The machine 1700 may include an outputcontroller 1728, such as a serial (e.g., Universal Serial Bus (USB),parallel, or other wired or wireless (e.g., infrared (IR), near fieldcommunication (NFC), etc.) connection to communicate or control one ormore peripheral devices (e.g., a printer, card reader, etc.).

The storage device 1716 may include a machine readable medium 1722 onwhich is stored one or more sets of data structures or instructions 1724(e.g., software) embodying or utilized by any one or more of thetechniques or functions described herein. The instructions 1724 may alsoreside, completely or at least partially, within the main memory 1704,within static memory 1706, or within the hardware processor 1702 duringexecution thereof by the machine 1700. In an example, one or anycombination of the hardware processor 1702, the main memory 1704, thestatic memory 1706, or the storage device 1716 may constitute machinereadable media.

While the machine readable medium 1722 is illustrated as a singlemedium, the term “machine readable medium” may include a single mediumor multiple media (e.g., a centralized or distributed database, and/orassociated caches and servers) configured to store the one or moreinstructions 1724. The term “machine readable medium” may include anymedium that is capable of storing, encoding, or carrying instructionsfor execution by the machine 1700 and that cause the machine 1700 toperform any one or more of the techniques of the present disclosure, orthat is capable of storing, encoding or carrying data structures used byor associated with such instructions. Non-limiting machine readablemedium examples may include solid-state memories, and optical andmagnetic media.

The instructions 1724 may further be transmitted or received over acommunications network 1726 using a transmission medium via the networkinterface device 1720 utilizing any one of a number of transferprotocols (e.g., frame relay, internet protocol (IP), transmissioncontrol protocol (TCP), user datagram protocol (UDP), hypertext transferprotocol (HTTP), etc.). Example communication networks may include alocal area network (LAN), a wide area network (WAN), a packet datanetwork (e.g., the Internet), mobile telephone networks (e.g., cellularnetworks), Plain Old Telephone (POTS) networks, and wireless datanetworks (e.g., Institute of Electrical and Electronics Engineers (IEEE)802.11 family of standards known as Wi-Fi®, IEEE 802.16 family ofstandards known as WiMax®), IEEE 802.15.4 family of standards,peer-to-peer (P2P) networks, among others. In an example, the networkinterface device 1720 may include one or more physical jacks (e.g.,Ethernet, coaxial, or phone jacks) or one or more antennas to connect tothe communications network 1726. In an example, the network interfacedevice 1720 may include a plurality of antennas to wirelesslycommunicate using at least one of single-input multiple-output (SIMO),multiple-input multiple-output (MIMO), or multiple-input single-output(MISO) techniques. The term “transmission medium” shall be taken toinclude any intangible medium that is capable of storing, encoding orcarrying instructions for execution by the machine 1700, and includesdigital or analog communications signals or other intangible medium tofacilitate communication of such software.

Each of these non-limiting examples may stand on its own, or may becombined in various permutations or combinations with one or more of theother examples.

Example 1 is a surgical device for evaluating soft tissue during asurgical procedure comprising: a pump to: inflate a first adjustablecomponent of an adjustable spacer to separate a femur and a tibia of aknee on a medial side of a patient; inflate a second adjustablecomponent of the adjustable spacer to separate the femur and the tibiaof the knee on a lateral side of the patient, the second adjustablecomponent independently adjustable to the first adjustable component;and during a range of motion test, maintain an equal pressure in thefirst adjustable component and the second adjustable component byallowing a medial gap distance between the femur and the tibia caused bythe first adjustable component or a lateral gap distance between thefemur and the tibia the second adjustable component to change; and aprocessor to: determine a maximum gap distance during the range ofmotion test; and output the maximum gap distance for display on a userinterface.

In Example 2, the subject matter of Example 1 includes, wherein the pumpis further to decrease the equal pressure during a repeated range ofmotion test.

In Example 3, the subject matter of Examples 1-2 includes, wherein theprocessor is to use a preoperative plan to determine the equal pressure.

In Example 4, the subject matter of Example 3 includes, wherein theprocessor is further to adjust the preoperative plan based on themaximum gap distance.

In Example 5, the subject matter of Examples 1-4 includes, wherein therange of motion test occurs after a tibial cut during a kneearthroplasty.

In Example 6, the subject matter of Examples 1-5 includes, wherein theprocessor is further to determine an implant based on a maximum medialgap distance and a maximum lateral gap distance, the implant having afirst height for the medial side and a second height different from thefirst height for the lateral side.

In Example 7, the subject matter of Examples 1-6 includes, wherein todetermine the maximum gap distance, the processor is to use opticaltracking of the femur and the tibia.

In Example 8, the subject matter of Examples 1-7 includes, wherein thesurgical device is a robotic surgical device, wherein the processoroperates a robotic controller, wherein the pump is controlled by theprocessor, and wherein the robotic surgical device includes a display,the display configured to present the user interface including themaximum gap distance.

Example 9 is a surgical device for evaluating soft tissue during asurgical procedure comprising: a pump to: inflate a first adjustablecomponent of an adjustable spacer to separate a femur and a tibia of aknee on a medial side of a patient; inflate a second adjustablecomponent of the adjustable spacer to separate the femur and the tibiaof the knee on a lateral side of the patient, the second adjustablecomponent independently adjustable to the first adjustable component;during a range of motion test, maintain an equal gap distance between amedial gap of the knee caused by the first adjustable component and alateral gap of the knee caused by the second adjustable component byincreasing or decreasing pressure in the first adjustable component orthe second adjustable component; a processor to: determine a maximumpressure during the range of motion test; and output the maximumpressure for display on a user interface.

In Example 10, the subject matter of Example 9 includes, wherein isfurther to decrease the equal gap distance and perform the range ofmotion test again.

In Example 11, the subject matter of Examples 9-10 includes, wherein theprocessor is to use a preoperative plan used to determine the equal gapdistance.

In Example 12, the subject matter of Example 11 includes, wherein theprocessor is further to adjust the preoperative plan based on themaximum pressure.

In Example 13, the subject matter of Examples 9-12 includes, wherein therange of motion test occurs after a tibial cut during a kneearthroplasty.

In Example 14, the subject matter of Examples 9-13 includes, wherein theprocessor is further to determine an implant based on a maximum medialpressure and a maximum lateral pressure, the implant having a firstheight for the medial side and a second height different from the firstheight for the lateral side.

In Example 15, the subject matter of Examples 9-14 includes, wherein todetermine the maximum pressure, the processor is to use optical trackingof the femur and the tibia.

In Example 16, the subject matter of Examples 9-15 includes, wherein thesurgical device is a robotic surgical device, wherein the processoroperates a robotic controller, wherein the pump is controlled by theprocessor, and wherein the robotic surgical device includes a display,the display configured to present the user interface including themaximum gap distance.

Example 17 is a method comprising: inserting a trial between a femur anda tibia of a knee, the trial including a medial spacer of a first heightand a lateral spacer of a second height differing from the first height;using a pressure sensor device, measuring pressure on a medial side ofthe knee and a lateral side of the knee throughout a range of motiontest with the trial in place; determining a maximum pressure during therange of motion test; and outputting the maximum pressure for display ona user interface.

In Example 18, the subject matter of Example 17 includes, decreasing thefirst height or the second height by replacing the medial spacer or thelateral spacer and performing the range of motion test again.

In Example 19, the subject matter of Examples 17-18 includes, using apreoperative plan to determine the first height and the second height.

In Example 20, the subject matter of Example 19 includes, adjusting thepreoperative plan based on the maximum pressure.

In Example 21, the subject matter of Examples 17-20 includes, performingthe range of motion test after a tibial cut during a knee arthroplasty.

In Example 22, the subject matter of Examples 17-21 includes,determining an implant based on a maximum medial pressure and a maximumlateral pressure, the implant having a first height for the medial sideand a second height different from the first height for the lateralside.

In Example 23, the subject matter of Examples 17-22 includes,determining the maximum pressure using an iAssist device.

Example 24 is at least one machine-readable medium includinginstructions that, when executed by processing circuitry, cause theprocessing circuitry to perform operations to implement of any ofExamples 1-23.

Example 25 is an apparatus comprising means to implement of any ofExamples 1-23.

Example 26 is a system to implement of any of Examples 1-23.

Example 27 is a method to implement of any of Examples 1-23.

Method examples described herein may be machine or computer-implementedat least in part. Some examples may include a computer-readable mediumor machine-readable medium encoded with instructions operable toconfigure an electronic device to perform methods as described in theabove examples. An implementation of such methods may include code, suchas microcode, assembly language code, a higher-level language code, orthe like. Such code may include computer readable instructions forperforming various methods. The code may form portions of computerprogram products. Further, in an example, the code may be tangiblystored on one or more volatile, non-transitory, or non-volatile tangiblecomputer-readable media, such as during execution or at other times.Examples of these tangible computer-readable media may include, but arenot limited to, hard disks, removable magnetic disks, removable opticaldisks (e.g., compact disks and digital video disks), magnetic cassettes,memory cards or sticks, random access memories (RAMs), read onlymemories (ROMs), and the like.

What is claimed is:
 1. A surgical device for evaluating soft tissueduring a surgical procedure comprising: a pump to: inflate a firstadjustable component of an adjustable spacer to separate a femur and atibia of a knee on a medial side of a patient; inflate a secondadjustable component of the adjustable spacer to separate the femur andthe tibia of the knee on a lateral side of the patient, the secondadjustable component independently adjustable to the first adjustablecomponent; and during a range of motion test, maintain an equal pressurein the first adjustable component and the second adjustable component byallowing a medial gap distance between the femur and the tibia caused bythe first adjustable component or a lateral gap distance between thefemur and the tibia the second adjustable component to change; and aprocessor to: determine a maximum gap distance during the range ofmotion test; and output the maximum gap distance for display on a userinterface.
 2. The surgical device of claim 1, wherein the pump isfurther to decrease the equal pressure during a repeated range of motiontest.
 3. The surgical device of claim 1, wherein the processor is to usea preoperative plan to determine the equal pressure.
 4. The surgicaldevice of claim 3, wherein the processor is further to adjust thepreoperative plan based on the maximum gap distance.
 5. The surgicaldevice of claim 1, wherein the range of motion test occurs after atibial cut during a knee arthroplasty.
 6. The surgical device of claim1, wherein the processor is further to determine an implant based on amaximum medial gap distance and a maximum lateral gap distance, theimplant having a first height for the medial side and a second heightdifferent from the first height for the lateral side.
 7. The surgicaldevice of claim 1, wherein to determine the maximum gap distance, theprocessor is to use optical tracking of the femur and the tibia.
 8. Thesurgical device of claim 1, wherein the surgical device is a roboticsurgical device, wherein the processor operates a robotic controller,wherein the pump is controlled by the processor, and wherein the roboticsurgical device includes a display, the display configured to presentthe user interface including the maximum gap distance.
 9. A surgicaldevice for evaluating soft tissue during a surgical procedurecomprising: a pump to: inflate a first adjustable component of anadjustable spacer to separate a femur and a tibia of a knee on a medialside of a patient; inflate a second adjustable component of theadjustable spacer to separate the femur and the tibia of the knee on alateral side of the patient, the second adjustable componentindependently adjustable to the first adjustable component; during arange of motion test, maintain an equal gap distance between a medialgap of the knee caused by the first adjustable component and a lateralgap of the knee caused by the second adjustable component by increasingor decreasing pressure in the first adjustable component or the secondadjustable component; a processor to: determine a maximum pressureduring the range of motion test; and output the maximum pressure fordisplay on a user interface.
 10. The surgical device of claim 9, whereinis further to decrease the equal gap distance and perform the range ofmotion test again.
 11. The surgical device of claim 9, wherein theprocessor is to use a preoperative plan used to determine the equal gapdistance and adjust the preoperative plan based on the maximum pressure.12. The surgical device of claim 9, wherein the range of motion testoccurs after a tibial cut during a knee arthroplasty.
 13. The surgicaldevice of claim 9, wherein the processor is further to determine animplant based on a maximum medial pressure and a maximum lateralpressure, the implant having a first height for the medial side and asecond height different from the first height for the lateral side. 14.The surgical device of claim 9, wherein to determine the maximumpressure, the processor is to use optical tracking of the femur and thetibia.
 15. The surgical device of claim 9, wherein the surgical deviceis a robotic surgical device, wherein the processor operates a roboticcontroller, wherein the pump is controlled by the processor, and whereinthe robotic surgical device includes a display, the display configuredto present the user interface including the maximum gap distance.
 16. Amethod comprising: inserting a trial between a femur and a tibia of aknee, the trial including a medial spacer of a first height and alateral spacer of a second height differing from the first height; usinga pressure sensor device, measuring pressure on a medial side of theknee and a lateral side of the knee throughout a range of motion testwith the trial in place; determining a maximum pressure during the rangeof motion test; and outputting the maximum pressure for display on auser interface.
 17. The method of claim 16, further comprisingdecreasing the first height or the second height by replacing the medialspacer or the lateral spacer and performing the range of motion testagain.
 18. The method of claim 16, further comprising using apreoperative plan to determine the first height and the second height,and adjusting the preoperative plan based on the maximum pressure. 19.The method of claim 16, further comprising performing the range ofmotion test after a tibial cut during a knee arthroplasty.
 20. Themethod of claim 16, further comprising determining an implant based on amaximum medial pressure and a maximum lateral pressure, the implanthaving a first height for the medial side and a second height differentfrom the first height for the lateral side.